Aux battery lifespan
Thread Starter
Newbie
Joined: Apr 2010
Posts: 8
Likes: 0
From: California
2006 E320 CDI
Aux battery lifespan
I have a 2006 E320 CDI, I have replaced the main (trunk) battery 3 times 2009, 2013 and 2019. Never replaced aux battery under hood, under cabin filter. It has to be at least 10 years old, maybe even original. This does not seem normal to me. What is this battery's lifespan. 10 years seems excessive. I have not had any warning about it.
MBWorld Fanatic!
Joined: Jan 2009
Posts: 9,225
Likes: 1,798
From: V E G A S
1922 Ford Model T / no OBD
Batteries are pretty tricky to test. I have resistor load tester and I have new Solar gizmo, who gives a spike to estimate CA on the battery.
It does happen that one will test the battery good, the other will fail it.
On other hand batteries are on reverse gear in technological progress.
When back in 1990's batteries could easy last over 10 years, when 13 or even 17 was reported, newer AGM batteries seem not to last more than 5 years.
I will not even say what newest energy recouping systems do to batteries.
So in W211 the aux battery never really works, unless there is big emergency, what seldom happens.
The controller checks the battery voltage, but doesn't check the battery capacity. Meaning 10 years old battery can still pass no-load voltage test, but will not have capacity to run much.
If you are risk-taker, you can drive with it till computer will give you a warning, but common between MB forum members is preemptive replacement.
When I usually object replacing parts who still might have 70% of life in them - not likely that apply to 10 y o battery. Shop around,.. I just order replacement aux battery for my W212, where it is used for engine ECO restarts.
FCP have MB brand batteries for slightly higher than other internet suppliers, but I generated free shipping and company advertise lifetime guarantee. As much as I am skeptic about company life, I figure out few buck extra is worth the try.
It does happen that one will test the battery good, the other will fail it.
On other hand batteries are on reverse gear in technological progress.
When back in 1990's batteries could easy last over 10 years, when 13 or even 17 was reported, newer AGM batteries seem not to last more than 5 years.
I will not even say what newest energy recouping systems do to batteries.
So in W211 the aux battery never really works, unless there is big emergency, what seldom happens.
The controller checks the battery voltage, but doesn't check the battery capacity. Meaning 10 years old battery can still pass no-load voltage test, but will not have capacity to run much.
If you are risk-taker, you can drive with it till computer will give you a warning, but common between MB forum members is preemptive replacement.
When I usually object replacing parts who still might have 70% of life in them - not likely that apply to 10 y o battery. Shop around,.. I just order replacement aux battery for my W212, where it is used for engine ECO restarts.
FCP have MB brand batteries for slightly higher than other internet suppliers, but I generated free shipping and company advertise lifetime guarantee. As much as I am skeptic about company life, I figure out few buck extra is worth the try.
Member
Joined: May 2011
Posts: 235
Likes: 23
From: Southern California
97 Lexus LS400, 04 Mustang, 08 Corvette Z51, 92 Honda Civic Si, 02 CL500, 03 E500
I replaced mine after 10 years. You can buy OEM at FCPEuro.com at reasonable price & it's lifetime warranty.
